The chamber has a double mantle through which cooling liquid (N2) passes. It is insulated outside and has a load lock system through which samples can be added or extracted during long-term experiments from an internal rotatable rack housing ten 30 cm high and 5 cm wide sample glass tubes. The rack is connected to an external motor, which via the control system can bring samples in position for UV radiation or for exchange during the experiment. The glass tubes are open at top and closed from the bottom with a metal plug containing a data logger. The data logger is connected to a thermo sensor, which allows continuous monitoring of the temperature at different depths in the sample during experiments.